Bug 1928254 - pt 1. Label arenas for the profiler r=glandium

Differential Revision: https://phabricator.services.mozilla.com/D227440

dom/base/DOMArena.h

@@ -10,6 +10,7 @@
 #include "mozmemory.h"
 
 #include "mozilla/mozalloc_oom.h"  // for mozalloc_handle_oom
+#include "nsString.h"
 
 #define NS_DECL_DOMARENA_DESTROY void Destroy(void);
 
@@ -34,10 +35,13 @@ namespace mozilla::dom {
 class DOMArena {
  public:
   friend class DocGroup;
-  DOMArena() {
+  explicit DOMArena(const nsACString& aLabel) {
+    nsCString label = PromiseFlatCString("DOMArena "_ns + aLabel);
+
     arena_params_t params;
     params.mMaxDirtyIncreaseOverride = 7;
     params.mFlags = ARENA_FLAG_THREAD_MAIN_THREAD_ONLY;
+    params.mLabel = label.get();
     mArenaId = moz_create_arena_with_params(&params);
   }
 

dom/base/DocGroup.cpp

@@ -128,7 +128,7 @@ DocGroup::DocGroup(BrowsingContextGroup* aBrowsingContextGroup,
   // mBrowsingContextGroup->mDocGroups as the caller does it for us.
   MOZ_ASSERT(NS_IsMainThread());
   if (StaticPrefs::dom_arena_allocator_enabled_AtStartup()) {
-    mArena = new mozilla::dom::DOMArena();
+    mArena = new mozilla::dom::DOMArena(aKey.mKey);
   }
 }
 

js/src/util/Utility.cpp

@@ -101,13 +101,16 @@ JS_PUBLIC_DATA arena_id_t js::StringBufferArena;
 void js::InitMallocAllocator() {
   arena_params_t mallocArenaParams;
   mallocArenaParams.mMaxDirtyIncreaseOverride = 5;
+  mallocArenaParams.mLabel = "JS malloc";
   MallocArena = moz_create_arena_with_params(&mallocArenaParams);
   BackgroundMallocArena = moz_create_arena_with_params(&mallocArenaParams);
 
   arena_params_t params;
   params.mMaxDirtyIncreaseOverride = 5;
   params.mFlags |= ARENA_FLAG_RANDOMIZE_SMALL_ENABLED;
+  params.mLabel = "Array buffer contents";
   ArrayBufferContentsArena = moz_create_arena_with_params(&params);
+  params.mLabel = "String buffer contents";
   StringBufferArena = moz_create_arena_with_params(&params);
 }
 

memory/build/mozjemalloc.cpp

@@ -1298,6 +1298,12 @@ struct arena_t {
   // released after a concurrent purge completes.
   bool mMustDeleteAfterPurge MOZ_GUARDED_BY(mLock) = false;
 
+  // mLabel describes the label for the firefox profiler.  It's stored in a
+  // fixed size area including a null terminating byte.  The actual maximum
+  // length of the string is one less than LABEL_MAX_CAPACITY;
+  static constexpr size_t LABEL_MAX_CAPACITY = 128;
+  char mLabel[LABEL_MAX_CAPACITY];
+
  private:
   // Size/address-ordered tree of this arena's available runs.  This tree
   // is used for first-best-fit run allocation.
@@ -1592,6 +1598,7 @@ class ArenaCollection {
     arena_params_t params;
     // The main arena allows more dirty pages than the default for other arenas.
     params.mMaxDirty = opt_dirty_max;
+    params.mLabel = "Default";
     mDefaultArena =
         mLock.Init() ? CreateArena(/* aIsPrivate = */ false, &params) : nullptr;
     mPurgeListLock.Init();
@@ -2940,8 +2947,9 @@ static inline arena_t* thread_local_arena(bool enabled) {
     // called with `false`, but it doesn't matter at the moment.
     // because in practice nothing actually calls this function
     // with `false`, except maybe at shutdown.
-    arena =
-        gArenas.CreateArena(/* aIsPrivate = */ false, /* aParams = */ nullptr);
+    arena_params_t params;
+    params.mLabel = "Thread local";
+    arena = gArenas.CreateArena(/* aIsPrivate = */ false, &params);
   } else {
     arena = gArenas.GetDefault();
   }
@@ -5004,9 +5012,22 @@ arena_t::arena_t(arena_params_t* aParams, bool aIsPrivate) {
 
     mMaxDirtyIncreaseOverride = aParams->mMaxDirtyIncreaseOverride;
     mMaxDirtyDecreaseOverride = aParams->mMaxDirtyDecreaseOverride;
+
+    if (aParams->mLabel) {
+      // The string may be truncated so always place a null-byte in the last
+      // position.
+      strncpy(mLabel, aParams->mLabel, LABEL_MAX_CAPACITY - 1);
+      mLabel[LABEL_MAX_CAPACITY - 1] = 0;
+      // In debug builds we assert if the string needed truncating.
+      MOZ_ASSERT(strlen(aParams->mLabel) < LABEL_MAX_CAPACITY);
+    } else {
+      mLabel[0] = 0;
+    }
   } else {
     mMaxDirtyIncreaseOverride = 0;
     mMaxDirtyDecreaseOverride = 0;
+
+    mLabel[0] = 0;
   }
 
   mLastSignificantReuseNS = GetTimestampNS();

memory/build/mozjemalloc_types.h

@@ -82,12 +82,17 @@ typedef struct arena_params_s {
 
   uint32_t mFlags;
 
+  // The label will be copied into fixed-size storage (currently 128 bytes)
+  // within the arena.  It may be null for unamed arenas
+  const char* mLabel;
+
 #ifdef __cplusplus
   arena_params_s()
       : mMaxDirty(0),
         mMaxDirtyIncreaseOverride(0),
         mMaxDirtyDecreaseOverride(0),
-        mFlags(0) {}
+        mFlags(0),
+        mLabel(nullptr) {}
 #endif
 } arena_params_t;